tigecycline resistant descendant of wild type R307
Freshly thawed isolates were subcultured on Columbia agar (Carl Roth GmbH + Co. KG, Karlsruhe, Germany) for 24h at 37 C before each experiment. The MIC was determined before and after the experiments using the broth dilution method according to the CLSI guidelines and EUCAST [20], [21] with freshly prepared [22] cation-adjusted Mueller-Hinton broth (Sigma-Aldrich, St. Louis, MO, USA). Tigecycline was purchased from The United States Pharmacopeial Convention , Rockville, MD 20852-1790, USA.